Field of the Invention
The present invention relates to an organic light emitting diode display device and more particularly to an organic light emitting diode display device having enhanced light extraction efficiency.
Description of the Related Art
An organic light emitting diode display device is a self-light emitting display device and, unlike a liquid crystal display, a separate light source is not required. Thus, the organic light emitting diode display device can be manufactured in a lightweight and thin form. Further, an advantage of the organic light emitting diode display device is that it is driven with a low voltage, which leads to lower power consumption. Also, the organic light emitting diode display device has excellent color expression ability, a high response speed, a wide viewing angle, and a high contrast ratio (CR). Therefore, the organic light emitting diode display device has been identified as a next-generation display device.
Light emitted from an organic light emitting layer of the organic light emitting diode display device passes through several components of the organic light emitting diode display device before being extracted to the outside of the organic light emitting diode display device. However, some light emitted from the organic light emitting layer is not extracted to the outside of the organic light emitting diode display device, but is, instead, locked in the organic light emitting diode display device. Therefore, the light extraction efficiency of the organic light emitting diode display device decreases.
Specifically, in a bottom emission type organic light emitting diode display device, approximately 50% of light emitted from the organic light emitting layer is locked in the organic light emitting diode display device due to total reflection or absorption by an anode electrode. Further, approximately 30% of light emitted from the organic light emitting layer is locked in the organic light emitting diode display device due to total reflection or absorption by a substrate. Thus, approximately 80% of the light emitted from the organic light emitting layer is locked in the organic light emitting diode display device and only 20% of the light is extracted to the outside. Therefore, the light extraction efficiency is very low.
In order to improve the light extraction efficiency of the organic light emitting diode display device, a micro lens array (MLA) on an overcoat layer of the organic light emitting diode display device, or a low index grid (LIG) structure, in which a plurality of low refractive index patterns spaced apart from each other are disposed on an anode electrode of the organic light emitting diode, may be formed.
However, even when a micro lens array is formed on the overcoat layer of the organic light emitting diode display device, a large quantity of light is locked in the diode, and the quantity of light extracted to the outside is small.
Further, when a plurality of patterns, which are spaced apart from each other, are disposed on the anode electrode of the organic light emitting diode, a non-emission area is generated and blurring and/or ghost phenomena are observed. Therefore, there is a demand for an organic light emitting diode display device which can solve the above-mentioned problems.